On Construction of Trajectory of Boxer’s Punch using a single IMU

In this work, we propose a system to construct the trajectory of punch for boxers. This system can plot trajectories of three kinds of punches including straight punch, hook, and uppercut via a single IMU sensor. A quaternion-based approach is utilized to identify rotations on collected data in three-dimensional space. Furthermore, we apply ellipsoid fitting as our calibration method to remove the built-in offsets inside the IMU sensor effectively. The experimental results show that the proposed system achieves reliable trajectories compared to the professional motion capture product, VICON Motion Systems. The root mean square error ($R M S E$) of trajectory in straight punch, hook, and uppercut are $0.041 \mathrm{~m}, 0.078 \mathrm{~m}$, and 0.117 m, respectively.